The proposed research will investigate the role of the pneumotoxic mechanism in resetting the termination of inspiration during sleep. Inspiratory inhibitory regions of the nucleus parabrachialis medialis will be lesioned and the respiratory pattern while awake and during sleep will be recorded after recovery. The pathogenesis of intermittent upper airway obstruction will be investigated using EMG methods to record activity of supralaryngeal muscles. The location and function of inspiratory "off-switch" neurons will be investigated. These neurons are presumed to receive inputs from vagal and intercostal afferents and from the pneumotoxic center, and they, in turn, project to medullary inspiratory neurons. BIBLIOGRAPHIC REFERENCES: Bartlett, D. Jr. and J.E. Remmers (1975). Reflex control of expiratory airflow and duration. J. Physiol. 247:22P-23P. Remmers, J.E., M. Putnam and D. Bartlett, Jr. (1975). Alterations in the respiratory pattern accompanying normal sleep in cats. Fed. Proc. 34:358.